Update, 10:50 p.m. EDT: The Centers for Disease Control and Prevention have now issued the first travel warnings for Mexico, due to swine flu. Its Web site reads: "At this time, CDC recommends that U.S. travelers avoid all nonessential travel to Mexico." The U.K. Foreign & Commonwealth Office is also advising against all but essential travel to Mexico at this time.

A travel "alert" posted this evening on the U.S. Department of State's Web site repeats the CDC's recommendation. However, the U.S. Department of State has not issued a direct warning or ban against travel to Mexico.

We have reached out to cruise lines that call on Mexico ports regarding potential changes to itineraries or cancellation policies in light of these new warnings. We'll keep you posted.

(6:10 p.m. EDT) -- Mexico travel warnings are on the horizon: This afternoon, Dr. Richard Besser, acting head of the Centers for Disease Control and Prevention (CDC), confirmed at a press conference that the federal government is preparing an advisory instructing Americans to avoid nonessential travel to Mexico, according to the Associated Press.

However, the official warning has not yet been issued, with the CDC, U.S. State Department and U.K. Foreign & Commonwealth Office all showing no changes on their respective Web sites at press time. The impact such a warning will have on cruises also remains to be seen.

At this point, cruise lines are still planning to call on Mexico ports. Princess, Holland America, Carnival, Fred. Olsen and Royal Caribbean Cruises Ltd. (parent of both Royal Caribbean and Celebrity) have all issued press releases throughout the day confirming that their itineraries remain unchanged, stressing that there have been no suspected cases of swine flu onboard or in Mexican cruise ports. (Norwegian Cruise Line, whose Norwegian Pearl is due into Cabo San Lucas on Friday, has not responded to our inquiries.)

Cruise Lines International Association (CLIA) -- which represents 24 cruise lines, including most of the above -- issued a similar statement today. It said that the cruise industry is "consulting closely with public health officials and government agencies" to monitor the situation, and that CLIA member cruise lines go to great lengths to maintain clean and sanitary environments. Interestingly, Princess' press release includes so much information on actions taken onboard -- from enhancing screening practices for passengers and crew boarding its ships to isolating those with suspect swine flu -- that it almost seems easier to just cancel the call.

The cruise lines have indicated that they will be communicating with passengers about swine flu (via avenues such as the daily newsletter), in an effort to make them aware of the risks and how to avoid contracting it. However, it seems that cruise ship crewmembers may not have gotten that memo just yet.

Cruise Critic Community Manager Laura Sterling is onboard Carnival Splendor this week with a group of nearly 200 Cruise Critic members and hosts, en route to Puerto Vallarta, Cabo San Lucas and Mazatlan. Since boarding yesterday, Sterling has approached staffers onboard to find out what Carnival was doing in light of swine flu concerns. "I stopped by Guest Services, posed my question and was met with a blank stare," she tells us via e-mail. "After explaining [to the crewmember], she still didn't know what I was referring to, but I received the standard answer: 'Any announcements made will be made over the main announcement system.'"

To be fair, the passengers onboard are not paying much mind to swine flu concerns, either. Sterling tells us that after sailaway last night, the mood onboard was jovial, and that the only talk of swine flu came in the form of jokes, such as, "Hey, don't sneeze on me!"

Sterling will be sharing updates from the ship throughout the week, keeping us posted on what's going on in terms of announcements and cruise travelers' concerns. Check out that thread, located at the top of the Carnival forum, often -- and stay tuned to Cruise Critic for the latest swine flu news as it pertains to cruise travel.

PLUS: Do you know fact from fiction when it comes to swine flu? We've published a Q&A with everything you need to know about the virus.